Hollywood actress Sigourney Weaver has been in the UK this week to promote her latest film Snow Cake. While in London she talked about her life, career and most famous role.

Weaver gave a talk this week at the Edinburgh Film Festival

Weaver will forever be associated with Ellen Ripley, the gutsy heroine from 1979 horror classic Alien and the three sequels in which she appeared.

It is a character that has come to define this statuesque New Yorker, whose screen career has been full of formidable, resourceful and fiercely intelligent roles.

She has been Oscar-nominated three times, notably for her forceful portrayal of scientist Dian Fossey in 1988 biopic Gorillas in the Mist.

The same year the Academy also shortlisted her for Working Girl, a movie that - like sci-fi spoof Galaxy Quest and the two Ghostbusters films - showcased her gift for comedy.

Last year she appeared in BBC Radio 4 play No Background Music as a former Vietnam nurse coming to terms with her past, and she will shortly be seen in UK cinemas playing an adult autistic in Snow Cake.

Eclectic career

Despite her prodigious output and diverse body of work, Weaver insists her eclectic career has developed organically in line with whichever projects come her way.

"I don't really sense I have a lot of control over it," she says.

Her best-known role remains Ellen Ripley in the Alien films

"Lately I've been doing more small films which I really enjoy. I come from off-Broadway theatre so the scale of independent films is perfect."

But smaller films bring their own worries, including money concerns. Snow Cake's shoot, for example, had to be put back after its financing fell through.

But Weaver says, "you can't be worried about that or you couldn't step out the door".

Nor does the prospect of tackling roles so dramatically removed from her own personality trouble her.

"But maybe one is more comfortable outside one's comfort zone because you're not yourself."

The actress cites her appearance as a former torture victim in 1994 film Death and the Maiden as one of her most challenging assignments to date.

'Over my head'

"I think that was the first time I was in territory where I felt over my head," she says of the Roman Polanski drama in which she co-starred with Sir Ben Kingsley.

"But you have to be willing to go as far out there as is accurate."

Her latest movie, Snow Cake, sees her playing a woman with autism

That certainly applied to her Snow Cake role. Weaver spent nearly a year preparing for the film, researching autism, visiting a specialist institute and living with a woman with the condition for a short period.

"I felt that if I really did the work and put in the time I could do it right," she says.

"It's a huge condition and there are about as many different manifestations as anything you can think of.

"The more I learned about it, the more I felt it was impossible to generalise," adds Weaver.

Over the next 12 months we will be seeing Weaver again in media satire The TV Set, Truman Capote biopic Infamous and political thriller Vantage Point.

But the actress says she will only return to outer space for another Alien adventure if the script is right.

"The chances of us doing it are slim," she says. "Nobody wants to do it unless it's really going to be original."